Quick-reset time-delay electronic control system



Jan. 31, 1950 R. B. J. BRUNN' QUICK-RESET TIMEDELAY ELECTRONIC CONTROL SYSTEM Filed Aug. 29, 1944 2 Sheets-Sheet l 4u aung muuaw mdE i I INVENTOR ROBERT B.J.BRUNN W Z? Jan. 31, 1950 R. B. J. BRUNN 2,495,919

QUICK-RESET TIME-DELAY ELECTRONIC CONTROL SYSTEM Filed Aug. 29, 1944 2 Sheets-Sheet 2 :Q (Q Q- 0 wu wd CD o l l u wd INVENTOR ROBERT B.J. BRUNN Patented Jan. 31,

Robert B. J. Brunn, Bayside, N Y., assignor, by

mesnc assignments, to flazeltine Research, Inc L,

Chicago, 111., a corporation of Illinois Applica i n A gust 2 4%.. Ser al N .5.1.33

8 Claims.

The present invention relates to quick-reset im -d la e e ron cen a s em n a ticularly, 'to such Systems which automatically reset themselves after each cycle of delayed control. While the control system oi the present invention is of general application, it is particularly suited for use in a protective system for electrical equipment and will be described in that connection.

There are many applications where it is desirable or necessary that electrical equipment be placed in service only after the lapse 'ofa certain time interval following the initial energiz ation thereof. A delay of this character may be neces. sary, for example, to enable either the equipment itself or "auxiliary equipment or both to reach a normal safe operating temperature prior to subjecting the equipment to normal load conditions. Illustrative of equipment of this class is the conventional cathode-ray tube which includes a fluorescent screen adapted to be scanned by an electron beam. The energy delivered to the screen of the tube by the electron beam is sufilcintly large that the screen is substantially damaged over any area thereof where the electron beam is allowed to rest for an appreciable short inter-val. This may occur, for example, during the normal warm-up period immediately fjollowing the energization of the cathode-ray tube and its associated scanning system, particularly where the cathode-ray tube and its associated powersupply system become fully operative before the vacuum. tubes of the scanning system have warmed up sufiiciently to generate scanning po-. tentlals or currents.

Of the numerous protective systems heretofore proposed for apparatus of the type men, tioned, a substantial number involve the use of electromagnetic relays. Such relays necessarily utilize movable parts and include some form of; electrical contact structure. These relays have numerous well-known disadvantages among the more important of which may be mentioned the prevalent tendency to fail due to sticking, dirty or burned contacts, to insulation breakdown, or to failure of their moving mechanical parts or the supporting bearings therefor. These relays have the additional disadvantage that their usefulness is usually restricted to those applications where the relay is not subjected in operation to shocks or vibration. Where it is necessary that the relay consume a minimum of power from its energizing control circuit, the relay must be so delicately constructed that its field of application is greatly lim ed.

T W91? h eums 41 sad a ta nh ren n elec qm saet c r are. t h been roposed that the d ire eentrel e e f cted elec mei ally by the use of vacuum tubes. Such electro ic contral sys ems of the ime-d la t e have n u uall been. t na l ap d w ielra i es t each a would enab e h cql ro syst m to n ra u c ss im -de a qet l mmedia el s a 91 9 Qt its est t on A $11b e...ie1 number 9f Ed Q' QQE QfiiF .9mm y tems Ki l or heir o er tion 11 the time tsl e ral rd f0}? e s m re WW I b9 5 t er o t0 at a n a tempera ure transmi tin h ir no ma perating temper ture Th let er r of i im ar e uit radi ns si e th t me re ay control provided thereby may change with the a or a si uqn. cf t e weird time as may be fi l j a t d y ses 9f n r z n QQW T se em a l e n t usual arab 9 ke t ics nc he e a ener s ored in one or more vacuum tubes thereof may be quite substantial It is an object of the present invention, there.- fore, to provide a new and improved quickreset time-delay electronic control system which avoids one or more of the disadvantages and limitations of prior control systems of; the type described,

It is a iurther object of the invention to provide a new and improved quick-reset time-delay electronic control system, the delay operation of which may be readily rendered responsive to one or to several operating conditions of apparatus controlled thereby and one thus having a high degree of flexibility of application.

It is an additional object of the invention to provide a new and improved quick-reset timedelay electronic control system of simple and inexpensive circuit arrangement comprising a minpossessing imurn' of circuit components yet one high stability and reliability of operation.

It' is a further object of the invention to provide anew and improved quick-reset time-delay electronic control system, the operation of which enables the attainment of a precise and accurate delay interval of selected value and an automatic reset action requiring a reset interval of precise value short in relation to the delay intervalf In accordance with the invention, a quick-reset time-delay electronic control system coin-1 prises a vacuum tube havin a first and a second operative state and including a control electrode which when energized maintains the vacuum tube in the first operative state, the vacuum tube in one of its operative states being adapted to provide a desired control effect. The system trode is energized from each thereof for limiting to a selected value the time interval of the energization of the control electrode to delay for this interval the establishment Of the second operative state of the vacuum tube. The control system additionally includes means effective upon the deenergization of the vacuum tube rapidly to restore the control of the time-constant circuit over th interval of energization of the control electrode.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

Referring now to th drawings, Fig. 1 is a circuit diagram, partly schematic, representing a complete radiant-energy transmitting system embodying the present invention in a particular form; Figs. 2, 4 and 5 represent simplified circuit diagrams of certain portions of the control system of Fig. 1 and are used to explain certain features of the control system and simplify an explanation of the operation thereof; and Figs. 3,

6 and '7 graphically represent operating characteristics of the control system in its simplified and complete forms.

Referring now more particularly to Fig. l of the drawings, there is represented a circuit diagram, partly schematic, of a complete radiantenergy transmitting system which includes a quick-reset time-delay electronic control system embodying the present invention in a particular form. Th transmitter includes a modulationsignal source II! which generates a modulation signal of periodic-pulse wave form. The output circuit of the unit It is coupled to an input circuit of a unit II which includes a quick-reset time-delay electronic control system I2, presently to be described in greater detail, a modulationsignal amplifier I3 having a signal-translating characteristic controlled by the control system 12, a second signal amplifier I4, and a modulator I5 having an output circuit coupled to a modulation input circuit of a wave-signal generator I6. The output circuit of the generator I5 is coupled to an antenna system H.

The transmitter is energized from a powersupply system I8 which includes a power transformer I9 having a primary winding coupled through a switch 2I to a source of alternating potential 22. The center-tapped secondary winding 23 of the transformer I9 is connected to a rectifier tube 24 in a conventional full-wave rectifier system which includes a series filter choke 25, shunt filter condensers 26, 21, and a bleeder resistor 21a. The transformer IS includes a low-voltage secondary winding 28 which is coupled to the heaters of the several vacuum tubes of unit II, as indicated by the reference character H in the drawing.

It will be understood that the transmitter just described is, with the exception of the control system I2 of unit II presently to be described, of conventional construction and operation, the

details of which are well understood in the art rendering further detailed description thereof unnecessary. Considering briefly, however, the operation of the transmitter as a whole, and neglecting for the moment the operation of the control system I2 of unit II, a modulation signal is supplied by the signal source ID to an input circuit of the unit II. The signal amplifiers I3 and I4 translate the applied signal to the modulator I5 which operates to apply a modulation signal of large current amplitude to the modulation input circuit of the wave-signal generator IS. The applied modulation signal modulates a wave signal enerated by the unit I6 and the modulated wave signal is applied to the antenna system I! for radiation therefrom. The operation of the power-supply system I8 is conventional, the transformer I9 being used to transform the relatively low-voltage alternating potential applied to the input terminals 22 to a high-voltage alternating potential which is rectified by the rectifier 24 and applied through the filter elements 25, 26 and 21 to the anode circuits of the vacuum tubes of unit I I. The winding 28 of the transformer I9 energizes the heaters of the latter vacuum tubes.

In order that the modulation signal applied to the modulation input circuit of the generator I6 shall have large current amplitude, the modulator 5 of unit II is a gaseous vacuum tube, for example a grid-controlled mercury-vapor tube marketed under the trade name Thyratron. The characteristics of this tube are such that the tube may be seriously damaged or its life appreciably shortened if a modulation signal is applied to its control electrode before its cathode has reached a normal operating temperature. A time interval of approximately twenty seconds is required between the moment when the power switch 2| of the power supply I8 is initially closed and the moment when the modulation signal may safely be applied to the control electrode of the vacuum tube I5. It is the purpose of the quick-reset timedelay electronic control system I2 of unit II so to controlthe characteristics of the signal amplifier I3 as to prevent the application of the modulation signal to the vacuum tube I5 for an interval sufficient to allow the cathode of the latter to reach a normal operating temperature after the switch 2! of the power-supply system I8 is closed to energize the transmitter.

' Considering now the portion of the system embodying the present invention, the quick-reset time-delay electronic control system I2 includes a vacuum tube 29 having a substantially inoperative state, or state of low conductivity, and an operative state or state of relatively high conductivity. This vacuum tube, which in its conductive state is adapted to provide a desired control effect for the signal amplifier I3 to control the amplification, of the latter, includes input electrodes comprising a cathode 30 and a control electrode 3I which when biased negatively to a predetermined value maintains the vacuum tube 29 in its inoperative or nonconductive state. The control system includes means for concurrently energizing the vacuum tube 29 and its control electrode 3| to initiate the establishment of the second or conductive operative state of this tube. This means comprises the power-supply system I8, which provides a high unidirectional potential for the anode of tube 29, and a cathode resistor 32 included in the cathode circuit of vacuum tube 29. The cathode resistor 32 has a small filter condenser 33 connected in shunt thereto. As will b c fully explained hereinafter, the cathode resistor is responsive to the space current flow through the vacuum tube .29 for energizing the control electrode 3| upon initiation of space current through this tube. The energizing circuit for the control electrode 3i includes, in addition to the cathode resistor 32 and in series therewith between the cathode 3G. and the filter choke 25., three series-connected resistors 34, 35 and 36 which are included in the negative-return lead of the power-supply system l8. and thus are common to the cathode circuits of all of the vacuum tubes of unit ll.

The energizing circuit last mentioned includes an electrical time-constant circuit for limiting to a selectedvalue the time interval of energization of the control electrode 3| to delay for this interval the establishment of the second operative state, or conductive state, of the vacuum tube 29 by the energizing means comprising the powersupply system l8. This time-constant circuit in cludes a condenser 31 for coupling the control electrode 3| of vacuum tube 29 to the junction of the filter choke and resistor 36, thus to couple the resistors 32, 34, 35 and 36 in series between the input electrodes 38 and 3| of the vacuum tube 29, and includes a resistor 38 connected in shunt to the input electrodes 38, 3|. As thus arranged, the resistors 32, 34, 35 and 36 essentially comprise a source of energizing potential for the control electrode 3| of vacuum tube 29 and the condenser 31 is included in series between the control electrode 3| and this source of enerizing potential.

The control system also includes means, comprising the condenser 3.1 and resistor 38, effective upon the deenergization of the vacuum tube 29 rapidly to restore the control of the time-constant circuit over the interval of energization of the control electrode 3|. This means comprises the series-connected resistors 32, 34, 35 and 36 which effectively. connect the condenser 31 across the input. electrodes 30 and 3| of vacuum tube 29 and which form with the condenser 31 a second timeconstant circuit. having a time constant much shorter than that of the condenser 31 and resistor 38.

The screen electrode of vacuum. tube .29 is connected directly to the cathode 30 of tube 29 so that the potential developed across the cathode resistor 32 when the vacuum tube 29 becomes conductive is applied as a positive energizing potential to the screen electrode of vacuum tube |3 to control the amplification of the latter. In partlcular, the vacuum tube l3 has little or no amplification during periods when its screen electrode has only a small or no potential applied thereto, as during the intervals when the vacuum tube 29 is nonconductive, but has high amplification during those intervals when the vacuum tube 29. becomes fully conductive to develop a substantial positive potential across the cathode resistor 32. I

In considering the operation of the control system just. described, it may be mentioned at the outset that the control action is divided into three general categories; namely, a control actlon responsive to the space current of all of the vacuum tubes l3, |4, |5 and 29., a control action responsive to. the space current of the vacuum tube 29. without regard to that of the. other vacuum tubes, and a control action which may be independent of the space current of any of the vacuum tubes. The simplified circuit diagrams of Figs. 2, 4 and 5 are used as an aid. in explain.

6 ing these several types of control action, the curves of Figs. 3, 6 and Z graphically representing the operating characteristics of the control system in its several simplified forms and in the form shown in Fig; 1.

Fig. 2 is a simplified circuit. diagram of a portion of the control system l2 of Fig. 1, simi lar circuit elements being designated by similar reference numerals, and is. used as an aid in explaining one. type of control action .efiected by the control system. In this simplified arrangement, the energizing circuit of the control electrode of tube 29 is shown as including a source of unidirectional energizing potential comprising a battery e. In the actual system of Fig. 1, no such battery is used but rather, as will be ex? plained more. fully hereinafter, the potential source 6 represents the. voltage developed across the resistor R which is comprised by the .resistors 34, 35 and 36 of Fig. 1. The anode of vacuum tube 29 is shown as energized through a switch S1 from a. source of anode potential, indicated as +3, and the. time-constant circuit 31, 38 is represented as coupling the input electrodes 39, 3| of tube 29 through aswitch S2 to the source of unidirectional energizing potentials. The switches S1 and S2, while they do not appear as such in the Fig. 1 system, represent the equivalent control effected by the power switch 2| of Fig. 1.. If the. switches S1 and S2 are closed simultaneously, and if it be assumed that the cathode 30 of the tube 29 is at normal operating potential, the condenser 31 will immediately begin to charge through the resistor 38 from the source. of potential e and, by virtue of the polarity of the potential source, will produce across the. resistor 38 a potential having negative polarity with re spect to ground. This potential is applied to the control electrode 3| of vacuum tube 29 and is effective to maintain the latter biased to anode current cutoff. As the condenser 31 becomes charged, its charging current begins to decrease, thus decreasing the voltage developed across the resistor 38. This continues until the condenser 31 is fully charged after a short interval. At the end of this interval, no voltage is developed across the resistor 38 and, there then being no bias upon the control electrode 3| of vacuum tube 29, the latter becomes fully conductive.

Curve. A of Fig. 3 represents the exponential manner in which the condenser 31 charges from the source of potential 6 and curve B represents the manner in which the negativ potential developed across the resistor 38 varies with time. The bias en atv which the vacuum tube 39 just becomes conductive is represented in Fig. 3 by the horizonta1 broken line. It will be apparent that the vacuum tube 29 is maintained in a noncon- .ductive state by the actionof the time-constant circuit 31, 38 during the interval lie-$1 and that this tube becomes fully conductive at time t2. If the switches S1 and S2 are opened at time t4, the condenser 31, which now biases the control electrode 3| positively with respect to. th cathode 30, is rapidly discharged during a relatively short interval til-t5 through a discharge path which includes the control electrode 3|, the cathode 38 and the resistor B. This rapid reset characteristic is represented by curve E.

The value of the resistor 38 is suiliciently large with relation to the capacitance of the condenser 31 that the latter requires several seconds to charge. The conductive resistance of the control electrode-cathode path of vacuum tube 29 and the resistance of the resistor R is sumciently small, on the other hand, that the condenser 31 discharges much more rapidly, for example within a second or less.

Fig. 4 is a simplified circuit diagram representing another portion of the control system l2 of Fig. 1, similar circuit elements being designated by similar reference numerals, and is used as an aid in explaining a second type of control action effected by the control system. If it be assumed that the cathode of the vacuum tube 29 is at normal operating potential at the moment the switch S1 is closed, the initial space current of the tube 29 flows through the cathode resistor 32 to develop thereacross a potential, positive with regard to ground. This initial space current remains small, however, since the potential developed across the resistor 32 immediately begins to charge the condenser 31 through the resistor 38, thus to develop across the latter a bias potential of negative polarity which is applied to the control electrode 3| of the vacuum tube 29 and is sufficiently large that it maintains the latter near anode current cutoff. As the condenser 31 charges, the charging current through the resistor 38 decreases so that the negative bias applied to the control electrode 3| also decreases to permit a slight increase in the space current of vacuum tube 29. This action continues until the condenser 37 becomes fully charged, at which time no potential is developed across the resistor 38 and the vacuum tube 29 is fully conductive.

In this type of control action, however, an appreciable time interval elapses before the vacuum tube 29 becomes fully conductive since the cathode resistor 32 effectively provides a degenerative control between the input and output electrodes of vacuum tube 29. Thus, as shown by curve C of Fig. 3, which represents the charging characteristic of the condenser 3'! in the Fig. 4 arrangement, the condenser 31 requires a relatively long interval tot3 within which to receive its full charge. Curve D of Fig. 3 represents the variation of voltage across the resistor 39. The Fig. 4 arrangement, like that of Fig. 2, also possesses the rapid reset feature. Thus, when switch S1 is opened at time t4, the condenser 3'! rapidly discharges, as represented by curve E, through a series circuit of relatively low resistance comprising the control electrode-cathode resistance of tube 29 and the cathode resistor 32. The control system is thus rapidly conditioned for another cycle of the operation described.

It can be shown mathematically that, during the charging interval of the condenser 31, the variation of potential of the cathode 30 of tube 29 may be expressed by the following relation:

ERR M B where iv-P C=capacitance of condenser 31 Rqa=resistance of resistor. 38

l as

Equation 1 is premised upon the assumptions that the value of the resistor 38 is very much larger than that of the cathode resistor 32 and, secondly, that the plate resistance R1) of tube 29 remains constant during the interval when the condenser 31 is receiving its charge. In connection with the second assumption, it will be evident that the value of potential drop developed across the cathode resistor 32 at any instant is dependent upon the plate resistance R of the tube 29, since it is the plate resistance of tube 29' and the resistance of the resistor 32 which de-' termine the value of space current flowing through the latter. That the second assumption is a reasonable one, however, will be apparent when it is considered that the value of resistance of the cathode resistor 32 is preferably at least eight to ten times larger than the plate resistance of the tube 29, so that variations of the latter become inappreciable in relation to the 'sum of the plate resistance and the resistance of resistor 32. Since the value of the resistor 32 is preferably many times larger than that of the plate resistance of vacuum tube 29, and since the amplification factor of tube 29 may be easily made to be of the order of 50 or more, Equation 1 may be simplified to the following approximate.

relation:

t E30:EB( 1 CRW) (2) It will be apparent that the first term of Equa' tion 2 represents the steady-state condition of the tube 29 following the interval required for the condenser 31 to charge. Similarly, the second term of Equation 2 represents a transient condition which governs during the interval when the condenser 31 is receiving its charge. It will be at once evident from this transient term that the degenerative control of tube 29 is ef-' Equation 1 shows that it is not only desirable to utilize a value of resistance for the resistor 32 large in comparison with the plate resistance of the vacuum tube 29 to render the ratio small, in that this ratio appears in the denomi nator of [3, but additionally that a large value of cathode resistance is desirable to enable the at" tainment of a large potential drop across thecathode resistor 32 during the steady-state condition of operation of the vacuum tube 29 after the condenser 31 has received its maximum charge, since the value of cathode potential is then almost equal to the potential of the source +B. Additionally, the larger the value of the cathode resistor 32, the larger will be the range of values over which the potential of the cathode 30 changes. This is of particular importance m the control system of Fig. 1 where the potential drop across the cathode resistor 32 is utilized to control the repeating ratio or gain of the con trolled amplifier l3. Thus, with a large value of cathode resistor, the relatively small value of the potential developed across the cathode resistor}? at the moment when the switch S1 is closed maybe: readily ascertained; from Equation: 2 to .have

the" following approximate value:

I In the simplified circuit diagram of Fig. 4, the source of potential +3 and the switch S1 together with the cathode resistor 32 comprise means for concurrently energizing the vacuum tube 29 and the control electrode 3| thereof to initiate the conductive state of operation of the vacuum tube. The condenser 3'! and. resister 33 comprise an electrical time-constant circuit included in the last-mentioned means for limiting to a selected value the time interval of energization of the control electrode 3| to delay for this interval the establishment of the conductive state of the vacuum tube by the energizing means. The resistor 32 and the electrodes 30, 3| of vacuum tube 29 comprise means effective upon the deenergization of the vacuum tube 29, as upon opening of the switch S1, rapidly to restore the control of the time-constant circuit 31, 38, by rapid discharge of the condenser 31, over the interval of energization of the control electrode 3|.

Fig. is a simplified circuit diagram in which the circuits of Figs. 2 and 4 are combined. The

, operation of this arrangement will be in general apparent from the foregoing described operation of Figs. 2 and 4. Referring to Fig. 6, the portion of the curve A between the time to when" the switches S1 and S2 are closed and the time t1 represents the control electrode-to-cathode voltage of the vacuum tube 29 produced by the potential drop across the resistor 38 due to the chargeof the condenser 31 from the potential source e. At time t1, the control electrode has insufficient bias to prevent the initiation of space current in the vacuum tube 29. A potential is thus developed across the cathode resistor 32, as represented by curve C. trode of tube 2.9, considered with relation. to ground potential, thus varies as representedby curve F during the interval t1-t3. The control electrode-to-cathode potential of vacuum tube 2 9' is equal to the difference at every instant be tween the values of curves C' and F and, hence, varies during the interval t1t3 as represented by curve A. From this, it will be evident that the Fig. 2 portion of the instant arrangement is effective to provide an. initial time delay during the interval to-t1, while the Fig. 4 portiono'f the instant arrangement is efiective to provide a much longer time relay extending from h to ta. In; the control system l2 of Fig. 1, therpotential developed across the resistors 34, 35 and 36 has been represented in. the simpiified circuit diagrams of Figs. 2, 4 and 5 as the potential e. A potential is developed across these resistors as soon as the rectifier tube 24 becomes conductive afterclosure'of the switch 2|, this potential being produced by the charging current of the filter condenser 2'! and the current of the bleeder resistor 21a. Curve G of Fig. 7 represents the manner of variation of the potential developed across the resistor 21a beginning at the moment to when the rectifier becomes conductive and curve H represents the manner of variationof the potential developed across the resistors 34, 35 and 36. v

The remaining curves A, C, E and F of Fig. 7 apply to the. operation of the control system 12 of Fig. 1 and correspond to curves bearing the samerdesignation in Figs. 3 and 6. The several The bias applied to the control elec- 7 tem'of the: Fig. lwarrangement will now be readily apparent from the curves of Fig. '7. Thus, the condenser 31 receives increasing values of charge during the time interval to-ti to maintain tube 29 biased to anode current cutofi 'as explained in regard: to the simplified arrangement of Fig. 2, this action continuing until the moment tz" when the vacuum tube 29 becomes slightly conductive. During the interval t2"t3", the control action is of the type explained hereinbefore in regard the simplified circuit arrangement of. Fig. 4. The control action during the entire interval to-'t3" is also dependent, at any given moment, to some extent upon. the space currents of all of the vacuum tubes |3., l4, l5. and 29 since this affects the'potentialr developed across the resistors 34, 3-5 and; 3-6,. the contribution of this factor to the control action depending in large extent upon the rapidity with which the cathodes of these tubes reach their normal operating temperatures after the. power-supply switch 2| is closed. Thus, the length of the interval t0"tz is dependent both upon the rapidity with which the vacuumv tubes reach normal operating: temperature and upon the time constant types of time delay provided by the. control sysof the condenser 3-! andv the resistor 38. The

length of the time interval t2"t3" depends, on the other hand, primarily upon the degenerative control of the tube 29 effected by the cathode resistor '32 andupon the time constant of the condenser 31 and resistor 38.

When the switch 2| is open to deenergize the power-supply system 18 as attime ii" of Fig. 7, the condenser 3T-rapidly discharges through the control electrode-to-cathode path of the vacuum tube 29 and through the resistors 32, 34, 35 and .36 rapidly to reset the control system I! at time ts. to conditionit fora subsequent cycle of timedelay control action, this rapid reset action being represented by curve E of Fig. 7. The rapidity of reset is determined, of course, by the value of capacitance of condenser 31, the value of the conductive resistance of the control electrode 3| and cathode 30 of tube 29, and by the values of the resistors 32, 34, 35- and 36. The values of resistance of these elements are so selected. that the total resistance of the discharge path. is only a small fraction of the value of resistance of resistor 38 so that the reset action requires an interval quite short with relation to the total time-delay interval provided by the control system upon energization of the latter.

While applicant ,doesnot intend to be limited to any particular circuit values in the embodiment of the invention. described, there follows a set of circuit values which have been found to be particularly suitable for a control system of the type-shown'in Fig. 1':-

Resistor 3B Condenser 33 Condenser 31 3.3 megohms 0.01 microfarad 0.5 microfarad Vacuum tube l3 Type 6AG5 Vacuum tube 14 Type 6J6 Vacuum tube l5 Type 21321 Vacuum tube 29 Type GAGE From the above description of the invention, it' will beapparent that a control system embodying the invention may be readily'rendered-responsive to one or to several operating conditions of an apparatus to be controlled by the system and is one thus having a high degree of flexibility of application. It will further be apparent that the control system of the invention is of simple and inexpensive circuit arrangement involving a minimum of circuit components and yet is one possessing a high degree of stability and reliability or" operation. The control system of the invention has the additional advantage that its time-delay and reset operations are controlled by electrical time-constant circuits which are so inherently stable as to enable the attainment of a precise and accurate delay interval of any selected value and an automatic reset action requiring a reset interval of precise value which is quite short in relation to the delay interval provided by the control system.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A quick-reset time-delay electronic control system comprising, a vacuum tube having a first and a second operative state and having a plurality of electrodes including a control electrode which when energized maintains said vacuum tube in said first operative state, said vacuum tube in one of its operative states being adapted to provide a desired control effect, means for concurrently energizing the electrodes of saidvacuum tube including said control electrode to initiate the establishment of said second operative state, means responsive to space current flow through said vacuum tube for additionally energizing said control electrode, said first-mentioned and second-mentioned energizing means including a common electrical time-constant circuit through which said control electrode is energized from each thereof for limiting to a selected value the time interval of said energization of said control electrode to delay for said interval the establishment of said second operative state of said vacuum tube, and means effective upon the deenergization of said vacuum tube rapidly to restore the control of said time-constant circuit over the interval of energization of said control electrode.

2. A quick-reset time-delay electronic control system comprising, a vacuum tube having a first and a second operative state and having a plurality of electrodes including a control electrode which when energized with a bias potential of predetermined polarity and magnitude maintains said vacuum tube in said first operative state, said vacuum tube in one of its operative states being adapted to provide a desired control effect, means for energizing the electrodes of said vacuum tube to initiate the establishment of said second operative state and for concurrently energizing said control electrode by applying thereto a bias potential having said predetermined polarity and at least said predetermined magnitude. means responsive to space current flow through said vacuum tube for additionally energizing said control electrode with a bias potential having said predetermined polarity, said first-mentioned and second-mentioned energizing means including a common electrical time-constant circuit through which said control electrode is energized from each thereof for limiting to a selected valuethe time interval of said energization of said control electrode to delay for said interval the establishment of said second operative state of said vacuum tube, and means efiective upon the deenergization of said vacuum tube rapidly to restore the control of said time-constant circuit over the interval of energization of said control electrode.

3. A quick-reset time-delay electronic control system comprising, a vacuum tube having a substantially inoperative state and an operative state and having a plurality of electrodes including a control electrode which when biased negatively to a predetermined value maintains saidvacuum tube in said inoperative state, said vacuum tube in one of its operative states being'adapted to provide a desired control effect, means for energizing the electrodes of said vacuum tube to initiate the establishment of said operative state and for concurrently energizing said control electrode by applying thereto a negative bias having said predetermined value, means responsive to space current flow through said vacuum tube for additionally energizing said control electrode with a negative bias potential, said first-mentioned and second-mentioned energizing means including a common electrical timeconstant circuit through which said control electrode is energized from each thereof for limiting to a selected value the interval of application of said bias to said control electrode to delay for said interval the establishment of said operative state of said vacuum tube. and means effective upon the deenergization of said vacuum tube rapidly to restore the control of said time constant circuit over the interval of energization of said control electrode.

4. A quick-reset time-delay electronic control system comprising, a vacuum tube having a first and a second operative state and having a plurality of electrodes including a control electrode which when energized maintains said vacuum tube in said first operative state, said vacuum tube in one of its operative states being adapted to provide a desired control effect, means for energizin the electrodes of said vacuum tube to initiate the establishment of said second operative state and including a source of bias potential for concurrently energizing said control electrode to maintain said vacuum tube in said first operative state, means responsive to space current flow through said vacuum tube for additionally energizing said control electrode, said first-mentioned and second-mentioned energizing means including a common electrical timeconstant circuit comprising a condenser in series with each of said energizing means and said control electrode and a resistor connecting said condenser across each of said energizin means for limiting to a selected value the interval of said energization of said control electrode to delay for said interval the establishment of said second operative state of said vacuum tube, and means effective upon the deenergization of said vacuum tube rapidly to restore the control of said time-constant circuit over the interval of energization of said control electrode.

5. A quick-reset time-delay electronic control system comprising, a vacuum tube having a first and a second operative state and having a pin rality of electrodes including input electrodes which when energized maintain said vacuum tube in said first operative state, said vacuum tube in one of its operative states being adapted to provide a desired control effect, means for energizing the electrodes of said vacuum tube to initiate the establishment of said second operative state and including an energizin circuit coupled between said input electrodes for concurrently energizing said input electrodes, said energizing circuit including a first and a second source of energizing potential of which said second source has a value of potential varying with the value of space current fiow through said vacuum tube and including an electrical timeconstant circuit having a resistor in shunt with said input electrodes and a condenser in series between each of said sources and said resistor for limiting to a selected value the interval of said energization of said input electrodes to delay for said interval the establishment of said second operative state of said vacuum tube, and means effective upon the deenergization of said vacuum tube rapidly to restore the control of said time-constant circuit over the interval of energization of said input electrodes.

6. A quick-reset time-delay electronic control system comprising, a vacuum tube having a first and a second operative state and having a plurality of electrodes including input electrodes which when energized maintain said vacuum tube in said first operative state, said vacuum tube in one of its operative states being adapted to provide a desired control efiect, means for energizing the electrodes of said vacuum tube to initiate the establishment of said second operative state and including an energizing circuit coupled between said input electrodes for concurrently energizing said input electrodes, said energizing circuit including a first and a second source of energizing potential of which said second source has a value of potential varying with the value of space current flow through said vacuum tube and including an electrical time-constant circuit having a resistor in shunt with said input electrodes and a condenser in series between each of said sources and said resistor for limiting to a selected value the interval of said energization of said input electrodes to delay for said interval the establishment of said second operative state of said vacuum tube, and a second time-constant circuit eifective upon the deenergization of said vacuum tube rapidly to restore the control of said first-mentioned time-constant circuit over the interval of energization of said input electrodes.

7. A quick-reset time-delay electronic control system comprising, a vacuum tube having a first and a second operative state and having a plurality of electrodes including input electrodes which when energized maintain said vacuum tube in said first operative state, said vacuum tube in one of its operative states being adapted to provide a desired control effect, means for energizing the electrodes of said vacuum tube to initiate the establishment of said second operative state and including an energizing circuit coupled between said input electrodes for con-- currently energizing said input electrodes, said energizing circuit including a first and a second source of energizing potential of which said second source has a value of potential varying with the value of space current flow through said vacuum tube and including an electrical timeconstant circuit having a resistor in shunt with said input electrodes and a condenser in series between each of said sources and said resistor for limitin to a selected value the interval of said energization of said input electrodes to delay for said interval the establishment of said second operative state of said vacuum tube, and a resistor coupling said condenser across said input electrodes and eiiective upon the deenergization of said vacuum tube rapidly to restore the control of said time-constant circuit over the interval of energization of said input electrodes.

8. A quick-reset time-delay electronic control system comprising, a first vacuum tube having a first and a second operative state and having a plurality of electrodes including input electrodes which when energized maintain said vacuum tube in said first operative state, a second vacuum tube coupled to said first vacuum tube to have an operating characteristic thereof controlled by one of the operative states of said first vacuum tube, means for energizing the electrodes of said first vacuum tube to initiate the establishment of said second operative state, means including a resistor in the cathode circuit of said first vacuum tube and a resistor common to the cathode circuits of both of said vacuum tubes for energizing said input electrodes, said last-mentioned energizing means including an electrical time-constant circuit having a condenser coupling said resistors in series between said input electrodes and having a resistor connected in shunt to said input electrodes for limiting to a predetermined value the interval of said energization of said input electrodes to delay for said interval the establishment of said second operative state of said first vacuum tube by said energizing means, and means effective upon the deenergization of said first vacuum tube rapidly to restore the control of said timeconstant circuit over the interval of energization of said control electrode.

ROBERT B. J. BRUNN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,728,745 Brown et a1. Sept. 17, 1929 1,946,615 Demarest Feb. 13, 1934 2,100,195 Lowry Nov. 23, 1937 2,279,007 Mortley Apr. 7, 1942 2,282,182 Gulliksen May 5, 1942 2,287,926 Zepler June 30, 1942 2,304,207 Richardson et a1. Dec. 8, 1942 2,354,086 Mackay July 18, 1944 

